So, I made hardtack recently. (originally from Comestible Zone)
Two cups of flour, one cup of water, a tablespoon of canola oil (didn't have any pig fat on me) was the recipe. Mixed it, flattened it, cut it into 12 four-inch squares, and baked at 300 F for an hour. Popped out, once nice and lightly brown.
Result: 12 rock-hard bricks. How the fuck did people eat this back in the day?